This study examined a possible association of the G>C polymorphism at
nucleotide -174 in the promoter region of the
interleukin-6 (IL-6) gene (rs1800795) with the prevalence of
diabetic complications in 235 patients with type 1 and 498 patients with
type 2 diabetes. Genotyping was performed using polymerase chain reaction (PCR) and subsequent cleavage by Nla III
restriction endonuclease. Analyzing all diabetic patients together demonstrated that 301 patients (41.1%) carried the GG genotype, 114 (15.6%) the CC genotype, and 318 (43.3%) were heterozygous for the GC genotype. However, there was no correlation of any of the genotypes with the prevalence of
diabetic nephropathy or
diabetic neuropathy, but subjects with the CC genotype had a significantly higher prevalence of
diabetic retinopathy compared to patients with the GC and GG genotype (p=0.016). This association was mainly lost when a logistic regression model was adjusted for diabetes duration (p=0.07). Consistently, a weak but not significant association of the polymorphism with
diabetic retinopathy was observed when type 1 and type 2 diabetic patients were analyzed separately (patients with
type 1 diabetes: p=0.12; patients with
type 2 diabetes: p=0.09). Analogically, no association of the polymorphism was found for
diabetic nephropathy or
diabetic neuropathy in these groups. In conclusion these data suggest no major influence of the -174G>C variant in the promoter region of the
IL-6 gene on the development of microvascular complications in patients with diabetes.